Update dataset API helpers and fix display bugs

src/api/dataset.ts

src/components/Corpus/Datasets/EditModal.vue

src/components/Corpus/Datasets/List.vue

src/components/Element/DetailsPanel.vue

src/components/Navigation/DatasetFromSelectionModal.vue

src/stores/dataset.ts

src/stores/elements.ts

src/types/dataset.ts

src/views/Dataset/Details.vue

tests/unit/stores/datasets.spec.js

tests/unit/stores/elements.spec.js